Air-spring



L. R. GRUSS.

AIR SPRING.

APmcAnoN mm APR.23,1911.

Patented June 15, 1920.

. 1N V ENTOR xms2/ j?, 6192253 UNITED STATES PATENT OFFICE.

LUCIEN R. GIB/USS, OF SAN FRANCISCO, CALIFORNIA, .SSIGNOR T0 PNEUMATIC CUSHION COMPANY, OF SAN FRANCISCO, CALIFORNIA, .A CORPORATION 0F Aarzomi.

.AIR-SPRING'.

Specification of Letters Patent.

Patented June 15, 1920.

Application led Apri123, 1917. Serial No. 163,831.

To all whom t may concern:

Be it known that I, LUCIEN R. GRUss, a citizen of the United States, residing at the city and county of San Francisco and State of California7 have invented new and useful Improvements in Air-Springs, of which the following is a specification.

rIhis invention relates to air springs of the type shown and described in mylprior Patents No'. 1,142,162, dated June 8th, 1915, and No. 1,216,254, dated February 13th, 1917.

The construction of these air springs embodies telescoping cylinders with a piston between them forming an upper chamber to contain air and a lower chamber to contain oil1 both chambers being variable in volumetric capacity, decreasing when the cylinders are moved together and increasing when the cylinders are moved apart. A seal of oil is maintained over the piston within the air chamber to prevent the escape of air. 0n the inward movement of the cylinders the inner end of the upper cylinder tting within the outer cylinder acts to displace oil in the lower chamber and if any excess oil be present therein by reason of leakage from the seal above, this leaked oil will be automatically returned to the seal. On the extension movement of the cylinders the capacity of the lower chamber will be increased, thereby creating` pressure vacuum which acts upon the cylinders to check the recoil.

As these air springs have been hitherto constructed, all air is expelled from the air chamber and forced into the cushion chaniber above before any oil is returnedto the seal, and the result is that an extra charge of air is admitted to the upper chamber each time the cylinders are moved to their approximate limit of inward movement. Therefore it sometimes happens that the quantity of air within the cushion chamber becomes excessive, necessitating the letting o of a portion thereof. Also at certain times in the operation of these air springs nothing but inelastic oil is present in the lower chamber which offers no cushioning action until a point is reached where the lower chamber is reduced in capacit-y to the volume of the body of oil. This may not occur within the limits of movement of the cylinders unless the seal has leaked out to some extent and thereby increased the volume of the oil below. It is desirable at times of extremely violent shocks tol augment the cushioning action of the upper chamber in order that the chambers may not be telesoped too far and permit overturningof the vehicle.

The present invention provides, first, for preventing the pumping upof the main compression chamber during the operation of the air spring, and, second, provides an auxiliary cushion of air below the piston in the lower chamber to aid the main cushion chamber, such auxiliary cushion coming into play only rwhen the cylinders are retracted to their approximate limit of inward movement so that when extremely violent shocks are imparted to the vehicle an additional load-supporting medium of compressible Huid will be present. By having an elastic medium on opposite sides of the piston the cushioning action of the spring is more resilient and yielding and the cylinders will be prevented from telescoping inwardly too far and thus endangering the equilibrium of the vehicle.

In carrying out this invention I arrange a cavity on the bottom of the piston in which air present in the oil chamber is trapped whenvthe oilV reaches a predetermined level, such air being compressed by the continued rise in the level of the oil as the cylinders move inward. The pressure of the air acts to resist the rise in the level vof the oil and thus serves to aid the main compression chamber in cushioning and supporting the load. The amount of air so trapped and compressed may be comparatively small and the increase and decrease in the volumetric capacity of the oil chamber such that upon extension movements of the cylinders the air present in the lower chamber and previously compressed in the cavity in the bottom of the piston will be so expanded as to be placed under tension and therefore will act with a suction to resist outward movement of the cylinders. In this way the recoil checking capabilities of the air springs as previously constructed are not interfered with.

By employing the auxiliary air cushion in conjunction with an air spring wherein a suction is present to check the rebound or retard the separating movement of the cylinders, a novel and advantageous result is accomplished in that when the springs are applied to a vehicle, those on the outside of the vehicle in rounding a sharp turn exert a Figs. 2 and 3 show detail sectional views taken inthe vicinity of the piston and illustrating the parts under different operating conditions. y

Fig. 4 shows the springs applied to a vehicle with the body of the latter tilted somewhat as in rounding a sharp turn.

The spring embodies an upper inner cylinder 10 and a lower outer cylinder 11 teleha lower chamber 16,

ttedtogether and closed at their opposite ends. A casing 12 is generallyprovided for the cylinders. rThe lower cylinder carries near its upper open end the piston 1?; lixed upon the upper end of a rod 14, the latter being secured to the bottom of the lower cylinder. rl`he piston 13 fits closely within the upper cylinder and divides the space within the two cylinders linto two chambers, namely, an upper chamber 15 and both being variable in volumetric capacity, decreasing in area when the cylinders are retracted and increasing in area when the cylinders are eX- tended. The variation in the capacity of the upper cylinder is due to the relative movement between the upper cylinder and piston, whereas the variation in the lower chamber is obtained by the displacement effected by the movement of the lower end of the upper cylinder within the cylinder 11.

The upper chamber 15 is supplied with air under pressure to support the load and forms the main cushion chamber of the device. The lower chamber 16 contains air largely and its main function is to check the recoil of the cylinders. It also serves as a collecting chamber for any oil leaking past the piston from the seal above, acting automatically by displacement to return such scopically leaked oil to the seal. The piston 13 is provided withV a cup leather 17 covering the upper face thereof and held in place by a cap 18 bolted to the piston rod. The cup leather has its 'flanges turned upwardly or toward the cushion chamber and pressing against the walls of the cylinder 10. A wall ot oil is normally present over the piston to seal the cup leather against leakage of air from the compression chamber.

T he lower end of the upper cylinder carries a leather packing 19 held in place by a ring 20 secured to the cylinder end. The

leather packing is cup-shaped and has its flanges turned downward to press against the walls of the outer cylinder to close the joint between the two cylinders against the escape oi oil from the chamber 16.

The piston is made concave at its bottom to form a dome-shaped cavity 21 abovethe pack joint and within this cavity any air present in the lower chamber is trapped when the level of the oil by reason of the displacement effected by the inward movement of the inner cylinder reaches a suliicient height to seal the rim of the piston head. As the cylinders continue to approach their limit of inward movement, the rise in the level of the oil is resisted by the pressure of the air in the cavity 21. There is thus formed an auxiliary cushion which aids the main cushion chamber to yieldingly support the load. Gradually there will be an equalization of pressure on the opposite sides of the piston, compression of the air in the cavity 21 being greater within a given movement of the cylinders than that of the air in the main compression chamber, on account of the small area of the cavity and the dome-shaped form thereof. lf oil has previously leaked out of the piston seal in suliicient amount to appreciably increase the volume of' oil in the lower chamber, then when an equalization of pressures above and below the piston occurs, the oil in the lower chamber will have reached the cup leather 17 and will pass between said cup leather and adjacent cylinder wall and enter the seal above.

The bottom of the piston may be itted with a flanged member 22 having. an extension 23 to telescope with the ring 20 when the two cylinders approach their outward limit of movement, the telescoping action of these parts forming a dash pot which cushions any tendency of the piston to strike forcibly against the ring under violent recoil. The flanged member 22 is spaced inwardly a slight distance from the walls of the cylinder 10 so that the oil trapped between the extension 23 and said cylinder walls may pass above the fla-nge to an annular space 24 below the piston packing. Extending from this annular space 24 to the interior of the cavity 21 are upwardly and inwardly inclined apertures 25 for the passage of air. By reason of this construction oil may be returned to the seal without necessitating the passing of air into the upper chamber.

In the operation, the device is attached to a vehicle, one cylinder to the body and the other to the running gear. The retracted cylinders are charged with a liquid such as oil which fills the lower chamber and extends into the upper chamber a few inches above the piston. The upper chamber is then'charged with air causing the cylinders CIT to move apart, thereby lifting the load and supporting it entirely upon the air cushion. The oil level in the lower chamber will be lowered by reason of' the withdrawal of the lower end of the inner cylinder therefrom and the oil above the piston will remain in place and form a seal for preventing the escape of air around the packing.

, In the normal operation, the shocks received by the vehicle will be absorbed by relative movements "of the cylinders to compress the air in the upper chamber more or less, the oil inthe lower chamber performing no cushioning function at this time. Whena violent shock is received, the cylinders are moved inwardly to their approximate limit of retraction and the displacement effected by the inner end of the upper cylinder will raise the level of the oil in the lower chamber, causing the air within to be trapped in the cavity 21. Continued inward movement of the cylinders will cause compression of the air within said cavity until a pressure is reached which equalizes the pressure on the opposite side of the piston. rThis air pressure in the cavity 21 will act upon the body of oil and assist in cushioning the load, whereas if air were not present on this side of the piston the oil itselt' would offer no cushioning function. Then the cylinders separate to any considerable extent upon the recoil the effect of the withdrawal of the lower end of the inner cylinder from the oil chamber is to increase the size of the chamber and this increase is such that the volume of air confined within the cavity 21 will be expanded so as to be under tension. The result of this will be a suction applied to the cylinders in such manner as to retard their separating movement which is exactly what is required to check the recoil and prevent tipping of the vehicle.

The presence of oil above the piston packfrom the compression chamber, but in time the oil will escape due to the constant pressure of the air within. The escaped oil will find its way into the lower chamber, thereby raising the level of the oil therein somewhat. At a subsequent time, when the cylinders are moved inwardly to their approximate limit of movement, the capacity of the lower chamber will be so decreased as to cause the displacement of' the oil around the piston, packing and into the upper chamber. lt wil1 be understood that the resistance ofli'ered oy the upturned flanges of the cup leather to the pas age of oil upwardly is considerably less than the resistance offered in the `ther direction. Consequently when the pressures on the opposite sides of the piston equalize the oil will readily and easily be lay-passed into the chamber above.

While the pressure imposed upon the body of oil in the lower chamber will be transmiting will serve to prevent the escape of airv ted to the packing 19 on the lower end of the inner cylinder, this will endure only tor an instant for the reason that the quantity of air or compressible fluid contained in the lower chamber is small as compared with the vohnne of' oil or non-coinpressible fluid therein, in consequence of which the pressure in the lower chamber is built up suddenly and just as quickly released. I rely upon the direction of the cup leather 19 to prevent loss of oilbetween the walls of the cylinders and find that it effectively accomlplishes this, inasmuch as the pressure applied thereto is of short duration. Leakage occurs only when a steady pressure is constantly. acting upon the oil, as in the case of the upper cushion chamber.

As will be seen in Fig. 4, the vehicle has a set of springs on opposite sides and in rounding a sharp corner the body inclines as shown. Therefore the springs on the inside will act by suction to pull the body back to normal level,the air in the lower chamber being at this time in tension on account oi the long separating movement of the two cylinders. At the same time the springs on the outside of the vehicle will act with all the resistance of the main and auxiliary cushion chambers and lift the body to normal level, the air being compressed in the cavity 21 at this time on account of the inward position of movement of the cylinders. As a result of this action of the springs there is small danger of the vehicle overturning in any emergency.

It is important to have the cavity 21 in the lower chamber of small capacity in order 4that only a small volume of air will be confined therein which will raise to very high pressures upon a smallrise in the level of the oil and also expand sufficiently to be placed in tension when the cylinders are moved apart to their approximate limit of outward movement.

Various changes in the construction and arrangement of the several parts herein shown and described may be employed without departing from the spirit of my invention as disclosed in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. An air spring having relatively moving members forming a main compression chamber to support the load, and means for establishing a sealed auxiliary compression when the members approach their limit of compressive movement whereby to assist the main chamber in supporting excessive loads.

2. An air spring comprising relatively moving members, a main compression chamber formed thereby to support the load, and an auxiliary oil sealed compression chamber formed by said members when they approach their limit of compressive moveme' t,

said auxiliary chamber acting in conjunction with the main chamber to support excessive loads.

8. In an air spring having relatively moving members forming the main compression chamber to support the load, means operable to establish an auxiliary oil sealed compression chamber when said members approach their limit of compressive movement and to create a suction acting to resist separating movement of the members when the latter approach their limit of expansive movement.

4l. In an air spring, telescoping cylinders having a piston dividing the interior into two chambers variable in volumetric capacity, one main chamber containing. largely compressible fluid to support the load and the other containing incompressible liquid and a compressible fluid to check the recoil, and means in conjunction with the lastnamed chamber Jfor compressing` the body of fluid to assist the main compression ch amber in vsupporting the load when the cylinders approach their limit of compressive movement.

5. In an air spring, telescoping cylinders having a piston dividing the interior into two chambers both variable in. volumetric capacity, one containing largely compressible fluid to support the load and the other containing incompressible liquid and a compressible fluid to check the recoil, and an auxiliary cliamber formed on the piston in which the compressible fluid is adapted to be trapped, compressed and sealed by the incompressible fluid when the cylinders approach their limit of compressive movement.

6. In an air spring, telescoping cylinders, the outer cylinder being disposed below and carrying a piston fitting within the upper cylinder, dividing` the interior into an upper chamber for air and oil and a lower chamber for air and oil, both variable in capacity when the cylinders are moved relatively, said piston at its lower side being formed with a cavity in which air is trapped, confined and sealed by the oil in the lower chamber when the cylinders approach their limit of inward movement, the construction being such that when the cylinders approach their limit of separating movement the air contained within said cavity will be expanded below atmospheric pressure whereby to exert a suction in a direction to restrain. an outward movement of the cylinders.

7. In an air spring, a pair of telescoping cylinders, a piston carried by one of said cylinders dividing the interior into two chambers, one main chamber containing largely compressible fluid to support the load and the other containing incompressible liquid and a small volume of air, an auxiliary chamber formed in the piston in communication with the small volume of air, said chamber forming a trap to permit the oil to compress and seal said air when the cylinders approach their limit of compressive movement whereby to assist the main chamber in supportino excessive loads and ports formed in the piston adapted to relieve a portion of the air admitted to the auxiliary chamber inthe piston.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

LUCIEN it. GRUSS. Witnesses:

Joriiv H. HERRING. W. W. HEALEY. 

